Refrigerating apparatus



Feb. 22, 1938. H. J. KRAcKowlzER A REFRIGERAIIING APPARATUS Fi'ld July25, 1936 .2 Ad EL m \\M B 7 Patented Febi' 1938 UNITED STATES PATENTori-"icl:

2,109,270 nEFmGEaA'rmG ArrARA'rUs Hermann J. Krackowizer, Chicago, Ill.

erating systems wherein liquid refrigerant is supplied to a duct or coilof the cooling unit to produce the cooling effect, and has referencemore particularly to a method of and facilities for improving theoperation `and increasing the efciency of such cooling by trappingliquid refrigerant in the duct or coil.

In refrigerating systems of the prevailing type', l0

er compression into liquid form is introduced through an expansion orcontrol valve into the duct' or coil of a cooling unit in which it isevaporated and converted to gas, thereby lowering the temperature of thecooling unit or coil by the absorption of heat which occurs in theconversion of the liquid into gas. Fromthe cooling unit the gas iswithdrawn by the compressor which re-converts the gas into liquid forre-circulation to and evaporation in the cooling unit.

Inasmuch as the eiiiciency of the cooling unit depends largely upon theamount of surface area upon which evaporation is taking place inside theduct or coil, it is important to maintain the largest possible area ofwet surface witllin the duct or coil while at the same time allowingample clearance for passage therethrough of the gas resulting fromevaporation. Moreover, in refrigerating systems of this character, it isthe practice to operate the compressor intermittently through automaticcontrols which cause the compressor to discontinue operation when thecooling unit andthe compartment in which'it is located have reachedpredetermined low temperatures and to resume operation upon apredetermined rise in temperature, and it not only is desirable tomaintain a suitable distribution of liquid refrigerant throughout thelength of the duct or coil, during operation of the compressor, g sothat evaporation and the cooling effect thereof are substantiallyuniform throughout the length ofthe duct or coil of the cooling unit,but it is also desirable, after the compressor is stopped, to retain inthe duct or coil an accumulation of liquid refrigerant which is suitablydistributed so that evaporation of liquid takes place uniformlythroughout the length of the duct or coil while the compressor isinoperative and when the compressor resumes operation the response inevaporation and cooling effect is similarly prompt and uniform -at allplaces throughout the duct n or coil.

Heretofore no convenient or satisfactory means has been available toinsure maximum wetting of the inside surfaces of the duct or coil of thea refrigerating medium is employed which aft- 193s, serial No. 92,515

(cl. a2-126)' cooling unit orto accumulate liquid refrigerant therein'sothat a Isupply remains uniformly distributed throughout the duct or coileither during operation of the compressor or after the operation thereofis discontinued, as the refrigerant, in previous ducts or coils and inthe succesf sive reaches thereof drained quite readily therefrom withthe result thatproper distribution of liquid refrigerant throughout theduct or coil and thorough wetting ofthe 'inside surfaces thereof was notassured, which in turn not only caused undesirable variations intemperature conditions at different places throughout the duct or coil,but also resulted :in irregular and ineiiicient compressor operation.

The principal objects of my -invention are to insure thoroughandouniform wetting of the inside surfaces of the duct or coil of thecooling unit of a refrigerating system; to avoid variations coil whichwould interfere with or ydiminish the flow of liquid or gaseousrefrigerant therethrough; and in general to provide simple, convenientand satisfactory facilities which will insure uniform and maximumwetting of the linside surfaces of the duct or coil of the cooling unitand otherwise increase the eiciency and impro-ve the operationthereof,-these and other objects being accomplished as will beapparentffrom the following description in which refer' 'ence is had tothe accompanying drawing, wherein:

Fig. 1 is a side view of a typical cooling unit embodying myimprovements;

Fig. v2 is an end view thereof looking at the right hand end of '.Eig.-1, with parts removed:

Fig. 3 is an enlarged vertical sectional view of a vertical return bendtaken on the line 3-3 of Fig. 2; and I Fig. 4 is an enlargedvertical'sectional. view of one of the horizontal return bends taken onthe line- 4 4 of Fig, 2 in which these return bends are at the remoteend of said Fig. 2 and shown therein in dotted lines. o

Referring to. the drawing, in which I have shown, for purposes ofillustration, a preferred embodiment of my-invention, the referencenumerati indicates the cooling unit as a whole which, in accordance withprevailing practice,

2' comprises a group of horizontal tubes 6 mounted in parallel relationand supported by Aend plates 'I and 6, said tubes having thereon closelyar-V which may be secured to the respective tubes 6 as at I I in anysuitable manner which will insure a leak-proof connection.

At the other end of the cooling unit one of the upper pipes 6 isprovided beyond the plate 6 with a fitting I2 by which it is connectedwith an expension or control valve Il through which liquid refrigerantis supplied from a compressor Il, it being understood, of course, thatthe usual condenser and receiver areinterposed in the line between thecompressor and expansionvalve I3 although not shown since theyform nopart of the present invention. One of the lower pipes 6 is providedbeyond the plate l with a union I5 by which it is connected with the.pipe I6 which leads to the intake side of the compressor I4, athermostatic bulb I1 being provided on the pipe I6 adjacent to thecooling unit 6 'as is customary and connected as at I8 with athermostatic device which regulates the expansion valve I6. The other1pipe ends beyond the plate 6 are connected in pairs by vertical returnbends I6 as best shown in Fig. 2 so that refrigerant entering throughthe expansion valve I3 passes successively through the two top pipes 6,then through the two pipes immediately therebelow, and so on down to thebottom pipes and from the final one of the latter to the pipe I6 whichreturns the evaporated refrigerant to the compressor.

In order to trap liquid refrigerant in each pipe, the horizontal 'returnbends yIII are offset upwardly as indicated at 20 and shown in Figs. 1,2, and 4 and the top portion of each vertical return bend I6 is offsetupwardly as indicated at 2I and shown in Figs. 1, 2, "and 3, preferablyto such an extent that the bottom oi' the passageway at the highest partof the rise or offset 20 or 2| of the respective return bend I0 or I9 isat the level of the top of the passageway of the tube 6 from which thatreturn bend leads, asis clearly shown in Figs. 3 and 4 by the dottedline 22. To accomplish the same trapping eilect in the last pipe 6 whichleads through the union I 5 and the return pipe I6 tothe compressor, theend of said pipe 6 may be turned up as shown at 2l and the adjoiningportion of the pipe I6 may be formed to provide a suitable bend 26 toafford with the bend 24 a rise corresponding to that of the offsets 2Iof the return bends I9 so that the outflow from the last pipe 6 iscontrolled in like manner and to the same extent as from the other pipes6.

Thus in the absence of some vcause such as release of gas yand flowthereof through the tubes 6., each tube 6 individually may accumulatetherein a quantity of liquid to a sufficient level to completely illlthe tube since the level at which each tube overflows substantiallycoincides with the top of the passageway through the tube. However, theamount of liquid refrigerant that will occupy each tube at a given time-will depend upon the relative rate of fiow of the liquid refrigerantthrough the expansion valve and evaporation thereof in the coil, and,moreover, as evaporation occurs in the tubes, the released gas willlower the level ofthe liquid to provide space for accumulation andoutflow of gas, and this effect will be cumulative in successive tubesin the respect that the liquid level in each succeeding tube will besuch as to accommodate the gas released therein and also that releasedin and passing therethrough from the preceding tubes. this trappingeffect of the rises 20, 2I and 24-26, however, being such, and the.supply of liquid refrigerant being preferably regulated so as tomaintain aquantity of liquid in all of the tubes 6.

'I'hus in each tube a substantial area of the tube surface is below thelevel of the liquid refrigerant trapped therein and, moreover, theturbulence of the liquid that occurs as evaporation ltakes place causesa wetting of' the tube surface above the liquid level and substantiallythe entire inside surface of each tube is thus maintained in a wetcondition so that .evaporation takes place in like manner over theentire inside surface of each tube and maximum heat absorption, as wellas uniform temperature condition of all the tubes, is thus assured.Moreover, upon interrupting theoperation of the compresser, since liquidrefrigerant has been accumulated in all the tubes, each tube not onlyhasa prolonged cooling effect, due to the presence of a quantity of coldliquid refrigerant therein, but the evaporation that occurs after thecom,- pressor has stopped is participated in by the liquid in all thetubes so that uniform heat absorp'tion conditions prevail throughout allthe tubes and there is accordingly no variation of tube temperature suchas occurs during the oif' cycle with other cooling units in which theliquid refrigerant at that time drains to and evaporates in the low'ertubes, thereby imparting to these lower tubes a lower temperature thanthat vof the upper tubes and causing a pocketing of the warmer gases inthe upper tubes. Furthermore, with my individually trapped tubearrangement, when the compressor resumes operation and pressure in thecoil is thereby reduced, the trapped ,refrigerantin each tubeimmediately and uniformly responds to the reduction of pressure and allthe tubes are accordingly uniformly and siy multaneously cooled.

Various means may be employed to accomplish the trapping effect of thedistorted return bends that are shown herein, as, for example, plainreturn bends may be employed instead of the oil'set return bends I0in-which case the offsetsin the return bends I9 will serve to accumulateliquid refrigerant in each pair of pipes that are at the same level, oreach tube 6 may slope upwardly to its outlet end so as to trap liquidtherein, or offsets may be provided in the tubes 6 instead of at thereturn bends,l or other fonns of return bends lmay be employed, or anyother -means may be provided to step up the duct or coil at suitableplaces or intervals to trap liquid in selected vparts of the duct orcoil. Also other types of cooling -units-or arrangements of coils ortubes may be employed, such for example as cast coils and either with orwithout ns as desired.

c Therefore, while I have shown and described my invention in apreferred form, I am aware vthat various changes and modifications maybe made without departing from the principles of my invention, the scopeof which is to be determined by the appended claims.

I claim as my invention:

1. A cooling unit having a pair of horizontal, laterally spaced tubes atthe same elevation, and la. return bend connecting corresponding ends ofthe tubes and having a passageway therethrough from one tube to theother, said passageway being elevated substantially midway be' tween thetubes to form a dam obstructive to flow of liquid from either tube tothe other.`

2. A cooling unit having a pair of horizontal, laterally spaced tubes atthe same elevation, and a return bend connecting corresponding ends ofthe tubes and having a passageway therethrough from one tube to theother, said passageway being elevated substantially midway between thetubes to the level of the top'of the tube openings to forni a damobstructive to ow of liquid from either tube to the other.

3. A cooling unit of the class described, comprising an upright group oftubes divided into pairs of substantially parallel' tubes, the membersof each pair of tubes being in a substantially horizontal plane, a bendconnecting the.

outlet end of the inlet tube of each pair of tubes to the inlet end ofthe discharge tube of the same pair of tubes and provided with anupwardly directed oiset, and an upright bend connecting the outlet endof each discharge tube of each pair of tubes to the inlet end of theinlet tube of the next adjacent lower pair of tubes and provided with anuprightly directed offset, the offset in the respective bendsconstituting dams obstructive to the ilow of liquid.

4. A cooling unit comprising an upright group of tubes divided intosubstantially horizontal pairs wherein the tubes of each pair are at thesame elevation, return bends connecting tubes of each pair at one end ofthe unit,each return Y bend being provided with an upwardly extendingoffset forming a dam obstructive to ow of liquid between said tubes, andupright return -bends connecting tubes at diierent elevations at theopposite end of the umt and provided with upwardly extending offsets toform dams obstructive to ow of liquid from the higher tube to the lowertube.

' HERMANN J. KRACKOWIZER.

